208 THE ANIMAL PARASITES OF MAN 



in scarlet fever Mallory's bodies, in hydrophobia Negri's bodies, in 

 trachoma Prowazek's bodies occur. 



(2) At first these characteristic cell-inclusions were considered to 

 be actual parasitic organisms causing the diseases in question. The 

 bodies received zoological names and attempts were made to work 

 out their supposed development cycles. The supposed parasites of 

 vaccinia and variola were referred to a so-called genus Cytoryctes, 

 those of hydrophobia to Neuroryctes, of scarlet fever to Cyclasterinm, 

 while those of molluscum contagiosum were referred to the Coccidia. 

 Calkins in 1904 studied in detail the cell-inclusions of vaccinia and 

 small-pox, calling them Cytoryctes variola, Guarnieri. Calkins con- 

 sidered that in the stratified cells of the epidermis they passed through 

 two cycles, the one cytoplasmic, the other intranuclear. The first is 

 the vaccinia cycle, the second the pathogenic (intranuclear) variola 

 cycle. It is hardly necessary to follow all Calkins' stages here. 



Negri (1909) described a cycle for Neuroryctes hydrophobia. Calkins 

 refers both Cytoryctes variola and Neuroryctes hydrophobia to the 

 Rhizopoda. 



Siegel (1905) described quite different organisms under the name 

 Cvtorhyctes. He listed several species : C. vaccinia of vaccinia and 

 small-pox, C. scarlatina of scarlet fever, C. luis of syphilis (this is 

 probably the granule stage of Treponema pallid urn), and C. aplitharum 

 of foot-and-mouth disease. 



(3) The afore-mentioned views were criticized, and the bodies 

 were not considered to be living organisms but merely reaction 

 products or cell-inclusions due to the effects of the virus on the host 

 cells. Thus Guarnieri's bodies were stated to consist of extruded 

 nucleolar or plastin material, having no developmental cycle. It was 

 further asserted that infection could be produced by lymph in which 

 Guarnieri's bodies had been destroyed. Similar assertions have been 

 made regarding the Negri bodies, and others. The Cytoryctes, 

 Ncuroryctes, etc., are considered, according to these views, to be 

 degeneration products of the nucleus or to be of a mucoid nature. 



(4) More recently a positive belief has gained ground that there 

 are true parasitic organisms causing these diseases, and that the 

 parasites are very minute, being termed Chlamydozoa by Prowazek 

 and Strongyloplasmata by Lipschutz. 



The Chlamydozoa are characterized by (a) their very minute size, 

 smaller than any bacteria, so that they can pass through bacterial 

 filters ; (b) they pass through intracellular stages, in the cytoplasm 

 or the nucleus of the host cell, producing therein the reaction 

 products or inclusions in the cell already recorded as characteristic 

 or diagnostic of the diseases produced; (c) they pass through definite 

 developmental cycles. Such a cycle consists essentially of growth 



